Resistively marked heating element and method for making same



Nov. 8, 1949 D E MARSH 2,487,064

RESISTIVELY MAR KED HEATING ELEMENT AND METHOD FOR MAKING SAME Filed May 2, 1947 '2" 7 9 ""ll"llIIllllIIllll|"IlllIllIllIIllII||llllllllflllllllmllllIIllIII|l|||lllllllllllllllllllllllllllllfllllfimmlllllflll "lllllllllll v l5 l2 1| IN VEN TOR.

. w L w Patented Nov. 8, 1949 aEsIsrrvELY HEATING ELEMENT MARKED AND METHOD FOR MAKING SAME Deloc E. Marsh, Kingsburg, can. assignor to C. A. Mlketta. Los Angeles, Calif.

Application May 2, 1947, Serial No. 745,688

1 This invention relates generally to a new article of manufacture, and methods of making same, and more particularly, to a supp wire for electrical heating made in the form of a long helical coil of heat-resistant, electrical resistance wiring (which may be of the nickel-chromium alloy type well known in the art), the entire length of such supply coil being marked at spaced points along its length in a manner correlated with the electrical resistance thereof, whereby a coil of a selected electrical resistance may be readily made by cutting of! from such supply coil a length indicated by the markings thereon.

The supply coil or wire of this invention is particularly adapted for use by electrical repairmen when called out on a repair job, such as for ex,- ample, replacing burned-out heating elements in electric ranges, hot plates, and various other electrical apparatus employing electrical heating elements therein. Heretofore, under such circumstances, it has been necessary that the repairman either carry pre-wound electrical heating elements along with him and cut them to the desired size on the job so that they will be may comprise either apparatus for measuring the linear length of the wire going into a coil wound on the job by the repairman or electrical measuring means such as an ohmmeter, or the like, for measuring the resistance of the prewound coils cut to size on the job or the coils wound on the job. In the first case, the measured linear length of wire forming the coil may be translated into the total electrical resistance by simple multiplication of the electrical resistivity of the wire per unit length by the length of the wire. It can be seen that this process of measuring the electrical resistance in order to arrive at a coil having the proper electrical resistance therein is a time-consuming operation, since repeated measurements will be necessary in order to approximate the desired overall electrical resistance in the coil.

The apparatus and method of my invention, however, make it possible for the repairman to either take along a prewound coil resistively visibly marked therealong so that the repairman may cut the coil at the appropriate marking or therebetween so that the coil will be 01' an overall 11 Claims. (Cl. 201-63) length such as to have the selected electrical resistance as indicated by the markings, or he may carry a spool of electrical resistance wire marked therealong in a manner correlated with the electrical resistance thereof and a suitable, portable coil-winding apparatus, which'may be of the type shown in my co-pending application Serial No. 745,667, filed May 2, 1947, now abandoned, or any other suitable portable type of coil-winding apparatus, and he may wind a coil on the job through the use of said wire and said winder, observing the markings on said wire, terminating the winding and severing the wire from the spool when the markings indicate that the coil has attained the desired electrical resistance.

Generally speaking, the apparatus of this invention comprises an electrical conductor carrying markings at points therealong in a manner correlated with the electrical resistance thereof, whereby said conductor may be made of a length, as indicated by said markings, such as to have a selected electrical resistance corresponding thereto.

Generally speaking, the method of this invention comprises marking an electrical resistance wire at points thereaiong in a manner correlated with the electrical resistance thereof, winding said marked wire into a coil and making said coil of a length, as indicated by said markings such as to have a selected electrical resistance corresponding thereto.

It can readily be seen that through the use oi the heating element of this invention and the method of making same, the work of the electrical repairman in replacing burned-out heat ing elements will be greatly facilitated.

With the above points in mind, it is an object of the present invention to provide a new and improved electrical heating element and method for making same wherein the coil is marked 11: a manner correlated with the electrical resistance thereof, whereby the coil may readily and simply be made of a length, as indicated by said mark ings, such as to have a selected electricai resistance.

It is a further object of this invention to providr a new and improved resistively marked electrics heating element which may be made to have i desired resistance without the necessity of meas' uring the actual electrical resistance thereof.

It is a further object of this invention to pro vide a method of making an electrical heatin: element of a desired electrical resistance withou the necessity of measuring the actual electrics resistance thereof.

Other and allied objects will become apparent tOthOSQSkflldililithBdl'tWflflWdlllQkamination and study of the illustrations, specification, and appended claims. To facilitate understanding, reference will be had to the following drawings, in which:

Fig. 1 is a view in elevation, partly broken away, illustrative of a spool mounting a length 01' electrical resistance wire thereon and showing the marked resistance wire extending therefrom.

Fig. 2 is a view illustrative 01' one embodiment of the electrical heating element of my invention. I

Fig. 3 is a view similar to that shown in Fig. 2 of a second illustrative embodiment of my invention.

Referring to Fig. 1, the spool I, which may be of any desired type, mounts a body 4 of electrical resistance wire 2 thereon with a portion of the electrical resistance wire 2 extending therefrom.

- The electrical resistance wire 2 is marked at points along its length. In the example shown, this marking comprises bandings, such as that indicated at 3, extending a short distance in a lengthwise direction and preferably circumferentially around the wire, it being understood that there are a plurality of such bandings 3 at spaced intervals along the wire 2. In the example described and illustrated, the markings 3 are applied at equal intervals along the wire by any suitable means such as a marking machine or they may be applied manually, if desired. The markings 8 may comprise a colored material, such as a colored varnish, shellac, or any other suitable material, applied to the wire, or other suitable means for identiflably marking the wire.

Referring to Fig. 2, the wire, indicated at 2', is wound into a long helical coil by means of any suitable coil-winding apparatus or by means of the portable coil-winding apparatus of my copending application, Serial No. 745,667, filed May 2, 1947. It will be noted that the spaced markings 3 on the wire 2 (as shown in Fig. 1) appear in the helical coil 5 as spaced markings therealong indicated at 3'. In the example described the markings 3 are equally spaced.

It will be apparent that if the repairman going out to replace a defective heating element carries a pre-wound element of the type shown in Fig. 2, he may make said element of the same electrical resistance as the element to be replaced by merely cutting the coil 5 at a point on or between the marking 3' corresponding to the desired electrical resistance as indicated by a conversion chart (not shown) indicating the electrical resistance for each unit of coil between adjacent markings 3 or indicating the required number or fraction thereof of said divisions between adjacent markings 3' required for a coil of a given wattage with a given electrical voltage source. While the coil is resistively marked, this may be converted into terms of wattage ii the voltage which is to be applied thereto is known.

Instead of the repairman taking along a. prewound coil of the type shown in Fig. 2 on a repair job, he may take along a spool of electrical resistance wire of the type shown in Fig. 1 and a suitable portable coil-winding apparatus. He may wind a coil of the requisite length so as to have a coil of the desired electrical resistance and electrical wattage rating by merely counting the bands 3' as they appear while winding the coil, ceasing said winding, and cutting the coil upon reaching the proper length.

Fig. 3 discloses a helical coil I wound from the electrical resistance wire 2" and having markings which in the example shown are indicated at 8. 8, II. H. II, and it. These markings may be ap plied to. the wire 2" forming the coil I in the same manner as that hereinbefore described. However, they are so arranged with respect to the electrical resistance of the wire that they indicate the total electrical resistance of the coil 1 from the marking 8 at the left-hand end thereof to the marking selected. As an example, the electrical resistance between the markings 8 and 9 might be such as to correspond to a wattage of 800 watts with the usual volts commercially available applied thereto. The electrical resistance between marking 8 and the marking i0 might be such as to correspond to 900 watts under the same circumstances. Markings Ii, l2, and il, similarly, respectively, might be such as to correspond to 1000 watts, 1100 Watts, and 1200 watts in the same manner. a

. The markings l0, ll, l2, and I3 are such as to be distinguishable from each other and from the markings 8 and 9, which, in the example shown, may be similar. The reason that the markings 8 and 9 are similar in the example shown is that they comprise the end markings of the coil indicating the maximum resistance and the minimum wattage of the coil. The arrangement of the markings 8, 8, i0, Ii, i2, 2*... l3 may be modifled within wide limits.

It should be noted that said markings actually indicate the electrical resistance from the lefthand end of the coil 1 to the marking selected. However, this corresponds to certain definite wattage values, as hereinabove explained, if the voltage applied thereto is known. If the repairman goes out on a call with a pre-wound coil of the type shown in Fig. 3, he may merely ascertain the wattage of the unit to be replaced and cut the coil 1 at the required marking or therebetween so as to obtain a coil having th required wattage rating.

The method of the present invention comprises marking a wire in a manner correlated with the electrical resistance thereof, winding said wire into a coil, and making said coil of a length as indicated by said markings such as to have a selected electric resistance. An illustrative form of this method is illustrated by the marked wire of Fig. 1 which is wound into a coil of the type shown in Fig. 2 and severed at the desired, point so as to obtain a coil of the desired electrical resistance and wattage.

Numerous modifications and variations of this invention will occur to those skilled in the art and are intended to be comprehended and included herein. For example, the markings on the wire and the way they are marked may be varied within wide limits. Under some circumstances it may be desirable to apply the markings after the coil is wound rather than apply same to the wire before winding the coil. It will be understood that th linear distance of the wire between markings applied on the coil subsequent to being wound may be readily determined from the number of loops of wire and the diameter of same between said markings. This is purely for purposes of calibration and it is not necessary to perform this calculation when using a coil. The electrical heating elements may take a form other than a helical coil, the only requirement being that the element occupy less linear length than the length of the wire composing it.

The examples described and illustrated herein are exemplary only and are not intended to limit the scope of this invention, which is to be inter preted in the light of the appended claims only.

I claim:

1. An electrical heating element comprising: a helically wound coil or electrical resistance wire having a predetermined electrical resistance per unit of length, said wire being visibly marked at successive points therealong in a manner correlated with the electrical resistance thereof, whereby said coil may be selectively cut to a length as indicated by said markings such as to have a selected electrical resistance corresponding thereto.

2. An electrical heating element of the character stated in claim 1, wherein each marking is indicative of the electrical resistance of the coil between it and the immediately preceding adjacent marking.

3. An electrical heating element of the character stated in claim 1, wherein the markings are equally spaced along the wire and each marking is indicative of the electrical resistance between adjacent markings.

4. An electrical heating element of the character stated in claim 1, wherein the markings are separately identifiable and each such marking along the coil is indicative of the total resistance of the coil to that point.

5. A method of winding a helically coiled electrical heating element of a selected electrical resistance from electrical resistance wire having a predetermined electrical resistance per unit length, comprising the steps of: visibly marking the wire at successive points therealong in a manner correlated with the electrical resistance thereof; winding said marked wire into a helical coil; and making said coil of a length indicated by said markings such as to have a selected electrical resistance corresponding thereto.

6. A method of the character stated in claim 5, wherein the marking operation is such as to mark the wire at equal intervals indicative of the electrical resistance between adjacent markings.

7. A method of the character stated in claim 5, wherein the marking operation is such that each of the markings is indicative of the total resistance of the wire to that point.

8. A method of winding a coil of a selected electrical resistance from electrical resistance wire having a predetermined electrical resistance per unit length, comprising the steps of: marking said wire at successive points therealong in a manner correlated with the electrical resistance thereof; winding said marked wire into a coil; and making said coil of a selective length as indicated by said markings such as to have a selected resistance.

9. A method of making a resistance unit of a selected electrical resistance from electrical resistance wire having a preselected electrical resistance per unit length comprising the steps of: marking said wire at equal points therealong in a manner correlated with the electrical resistance thereof; and forming said marked wire into a resistance unit of a length as indicated by said markings such as to have a selected electrical resistance.

10. An electrical resistance unit comprising: a coil of electrical resistance wire having a predetermined electrical resistance per unit length, said wire being circumferentially marked at points therealong in a manner correlated with the electrical resistance thereof whereby said coil may be made of alength as indicated by said markings such as to have a selected electrical resistance.

11. An electrical conductor carrying circumferentia1 markings at points therealong in a manner correlated with the electrical resistance thereof, whereby said conductor may be made of a length as indicated by said markings such as to have a selected electrical resistance corresponding thereto.

DELOS E. MARSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

